Captive type sparkplug gasket

Abstract

A captive spark plug gasket in which the means for maintaining the captive relation is in the form of an inwardly directed flange, the free edge of which is provided with a plurality of staked undulations to provide the equivalent of metal which is appreciably thicker than the original thickness of the metal stock from which the gasket is formed. During a staking operation, the inwardly directed flange is inwardly folded to reduce the effective diameter of the free edge thereof, so as to be positioned to lie upon the unthreaded undercut area adjacent the lower transverse surface of the plug body. Because of the increased thickness of the free edge of the inwardly folded flange, cross threading with respect to the thread on the shank does not occur when the plug is unthreaded from an engaged cylinder head opening, and the gasket remains captive on removal.

I claim 
     
       1. In a combination spark plug and captive gasket therefor, in which said spark plug includes a plug body having a threaded shank portion extending outwardly from a main body portion, said threaded shank portion including an undercut area adjacent said main body portion, said gasket including a plurality of mutually compressible flanges and a locking flange extending inwardly of said compressible flanges to be engaged wihin said undercut area, said locking flange having a free generally arcuate edge, said threaded shank having a given pitch and defining a continuous spiral recess between adjacent convolutions of thread, the improvement comprising: said arcuate free edge of said locking flange having at least one offset staked area wherein the effective width of said edge at said area is substantially greater than the thickness of metal forming said locking flange; whereby said offset staked areas are prevented from cross-threading the thread on such shank portion to thereby prevent an installed spark plug from becoming unthreaded from a threaded spark plug opening while simultaneously disengaging said gasket from said plug. 
     
     
       2. Structure in accordance with claim 1, further characterized in said staked areas being positioned at arcuate intervals of 90°.